(1) Field of the Invention
The present invention relates to an evaporation pressure control device for a refrigeration cycle, especially for a refrigeration cycle of an air conditioning system of an automotive vehicle.
(2) Description of Prior Art
In a refrigeration cycle of an air conditioning system of the type, in which lubricating oil for lubricating a compressor circulates through the refrigeration cycle together with refrigerant, when the air conditioning system is operated with shortage of the refrigerant resulting from the leakage thereof the amount of the lubricating oil as well as the refrigerant returning to the compressor decreases because of impounding in various parts of the refrigeration cycle, whereby the temperature of the compressor increases.
Especially, in such a refrigeration cycle as has an evaporation pressure control valve, when the pressure of the refrigerant out of an evaporator decreases because of the leakage of the refrigerant, the control valve is kept closed to stop returning of the refrigerant and the lubricating oil to the compressor, resulting in seizure in the compressor.